University of Tasmania
Browse

File(s) under permanent embargo

The Dovyren intrusive complex (northern Baikal region, Russia): Isotope-geochemical markers of contamination of parental magmas and extreme enrichment of the source

journal contribution
posted on 2023-05-18, 15:57 authored by Ariskin, AA, Leonid Danyushevsky, Konnikov, EG, Maas, R, Kostitsyn, YA, Andrew McNeill, Sebastien MeffreSebastien Meffre, Nikolaev, GS, Kislov, EV
The Dovyren intrusive complex includes the ore-bearing (Cu–Ni–PGE) Yoko–Dovyren layered pluton (728 Ma, up to 3.4 km in thickness), underlying ultramafic sills, and comagmatic leuconorite and gabbro-diabase dikes. Studies of Sr–Nd–Pb isotope systems were carried out for 24 intrusive rocks and five associated low- and high-Ti basalts. The high-Ti basalts show 0.7028 ≤ (87Sr/86Sr)T ≤ 0.7048 and 4.6 ≤ εNd(T) ≤ 5.8, similar to the values in MORB. The intrusive basic and ultrabasic rocks are geochemically similar to the low-Ti formation, making a compact cluster of compositions with extremely high ratios of radiogenic Sr and Pb isotopes and low εNd values. The maximum enrichment in radiogenic Sr is shown by the rocks near the pluton bottom ((87Sr/86Sr)T = 0.71387 ± 0.00010 (2σ); εNd(T) = –16.09 ± 0.06), which are the products of crystallization of the most primitive high-Mg magmas. The above-located dunites, troctolites, and gabbro show lower enrichment, probably because of the contamination of the host rocks during the filling of the magma chamber and/or because of the slight heterogeneity of the source. Calculations of the proportions of mixing of the parental melt with carbonate terrigenous material have shown that the variations in the Sr and Nd isotope ratios are due to the incredibly high contamination of the sediments, up to 40–50%. This contradicts the succession of the main rock types in the Yoko–Dovyren pluton in accordance with the crystallization of picrite-basaltic magma. The contribution of 5–10% high-Ti component seems more likely and suggests interaction between two isotopically contrasting magmas in this province in the Late Riphean. In general, the minor variations in εNd(T) of the intrusive rocks and metavolcanics (–14.3 ± 1.1) testify to the isotopically anomalous source of the low-Ti magmas. The time variation trend of εNd and geochemical features of the Dovyren rocks indicate that the products of melting of 2.7–2.8 Ga suprasubduction mantle might have been the massif protolith. Thus, the Dovyren parental magmas formed from a much older (sub)lithospheric source in the Late Riphean. The source was initially enriched in a mafic component with a low Sm/Nd ratio and was isolated from the convecting mantle and mantle melting processes for ~ 2 Gyr. The existence of such a long-living and at least twice reactivated lithospheric substratum is confirmed by the fact that the Nd isotope evolution trend of the initially nonanomalous mantle protolith includes not only the Dovyren rocks but also the Paleoproterozoic gabbro of the Chinei pluton and the Archean enderbites of the Baikal region.

Funding

Australian Research Council

AMIRA International Ltd

ARC C of E Industry Partner $ to be allocated

Anglo American Exploration Philippines Inc

AngloGold Ashanti Australia Limited

Australian National University

BHP Billiton Ltd

Barrick (Australia Pacific) PTY Limited

CSIRO Earth Science & Resource Engineering

Mineral Resources Tasmania

Minerals Council of Australia

Newcrest Mining Limited

Newmont Australia Ltd

Oz Minerals Australia Limited

Rio Tinto Exploration

St Barbara Limited

Teck Cominco Limited

University of Melbourne

University of Queensland

Zinifex Australia Ltd

History

Publication title

Russian Geology and Geophysics

Volume

56

Pagination

411-434

ISSN

1068-7971

Department/School

School of Natural Sciences

Publisher

Elsevier BV

Place of publication

Netherlands

Rights statement

Copyright 2015 V.S. Sobolev IGM, Siberian Branch of the RAS.

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the earth sciences